Pushing the Boundaries of Photovoltaic Light to Electricity Conversion: A GaAs Based Photonic Power Converter with 68.9% Efficiency - Helmers, H; Lopez, E; Höhn, O; Lackner, D; Schön, J; Schauerte, M; Schachtner, M; Dimroth, F; Bett, AW (Conference Record Of The Ieee Photovoltaic Specialists Conference, 2021)